1. Field of Disclosure
The present disclosure relates generally to data compression technologies, and more specifically to obtaining enhanced compression in representing non-edge blocks of image frames.
2. Related Art
Image frames are often represented in compressed form. For example, a sequence of image frames are generated from a video signal capturing a scene of interest, and the frames are compressed, typically either for reducing storage space or for reducing transmission bandwidth requirements. H.264, described in further detail in “Information technology—Coding of audio-visual objects—Part 10: Advanced Video Coding”, available from ISO/IEC (International Standards Organization/International Electrotechnical Commission), is an example approach using which image frames are represented in compressed form.
Blocks are often used as a basis for compression of image frame. For example, in the H.264 standard noted above, a frame is divided into blocks of (4×4, 8×8 or 16×16 pixels) size. However, the blocks can be of other shapes (e.g., rectangle or non-uniform shape) and/or sizes in alternative standards. For clarity, the term source block is used to refer to uncompressed representation and compressed block is used to refer to compressed representation.
Typically, a predicted block is generated associated with each source block using a prediction mode, and the compressed representation is generated as a difference of each corresponding pixel of the predicted block and the source block. H.264 standard refers to prediction modes such as horizontal prediction mode, vertical prediction mode, etc., in which adjacent pixels (immediately left and/or above) are used to predict each pixel of the predicted block according to the prediction approach.
Each image frame may be viewed as containing blocks at the frame edges and non-frame-edges. A frame-edge block refers to a block, which has at least one pixel at the boundary of the image frame. A non-frame-edge refers to a block, which does not have any pixels at the boundary of the image frame. As may be appreciated for a frame having (A×B) pixels, there would be a total of (2A+2B−4) pixels at the boundary.
At least as image frames need to be represented in compressed form, there is a general need to represent non-frame-edge blocks also in compressed form. It is often desired that the compression be enhanced so that the number of bits used in representing the data is correspondingly reduced.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.